1. Technical Field
The present invention relates to a color filter ink, a color filter ink set, a color filter, an image display device, and an electronic device.
2. Related Art
Color filters are generally used in liquid crystal display devices (LCD) and the like that display color.
Color filters have conventionally been manufactured using a so-called photolithography method in which a color photoresist composed of a material (color layer formation composition) that includes a colorant, a photosensitive resin, a functional monomer, a polymerization initiator, and other components is formed on a substrate; whereupon photosensitive processing for radiating light via a photomask, development processing, and the like are performed. In such a method, the color filters are usually manufactured by repeating a process in which a color photoresist corresponding to each color is formed on substantially the entire surface of the substrate, only a portion of the color photoresist is cured, and most of the film other than the cured portion is removed, so that there is no color overlap. Therefore, only a portion of the color photoresist formed in color filter manufacturing remains as a color layer in the finished color filter, and most of the color photoresist is removed in the manufacturing process. Accordingly, not only does the manufacturing cost of the color filter increase, but the process is also undesirable from the perspective of resource saving.
Methods have recently been proposed for forming the color layer of a color filter through the use of an inkjet head (droplet discharge head) (see Japanese Laid-Open Patent Application No. 2002-372613, for example). In such a method, because the discharge position and other attributes associated with droplets of the material (color layer formation composition) used to form the color layer are easily controlled, and waste of the color layer formation composition can be reduced, the environmental impact can be reduced, and manufacturing cost can also be minimized.
However, in a method for manufacturing a color filter using an inkjet head, when droplets are discharged for long periods of time, the droplet discharge quantity becomes unstable, the trajectory of the discharged droplets changes (so-called flight deflection occurs), it becomes impossible to land the droplets in the desired region, and other problems occur. When such problems occur, the color saturation fluctuates between the plurality of colored portions that are originally supposed to have the same color saturation, and on the substrate or the like onto which the droplets are to be discharged, the plurality of types of ink used to form different colored portions mixes together (colors mix), and as a result, uneven color between regions of the same color filter, uneven saturation, and the like occur, fluctuation occurs in the characteristics (particularly contrast ratio, color reproduction range, and other color characteristics) between numerous color filters, and the reliability of the color filters is reduced. Such problems are particularly severe when a material that includes a pigment is used as the material for forming the color layer. Since the droplet discharge device (industrial) used for color filter manufacturing is entirely different from what is used for a printer (consumer-level), and the droplet discharge device is used for mass production and droplet discharge onto large-scale workpieces (substrates), for example, there is a need to discharge large quantities of droplets for long periods of time. Because the droplet discharge device is used under such harsh conditions, the droplet discharge quantity is more prone to vary than in a consumer printer, but when such variation in the discharge quantity occurs, fluctuation occurs in the characteristics between the numerous manufactured color filters, fluctuation occurs in the color saturation between regions of the same color filter, and the reliability of the color filter as a product is severely reduced.
Inks having a high colorant content have recently been used as color filter inks in order to ensure a higher color reproduction range and higher contrast ratio in a color filter, but such problems as those described above become more severe the higher the content ratio of the colorant (particularly pigment) becomes.
There has also been a recent trend of increasing the luminance of the displayed image in liquid crystal display devices (LCD) and the like for color display in order to achieve even higher picture quality. Such increased luminance creates a need for enhanced color filter durability.